Rotor magnet positioning device

ABSTRACT

A device for positioning a planar array of magnets within a permanent magnet electrical machine of the type having a rotor and stator with an air gap there between. The device includes a body made of non-ferrous material and having a first side which is attachable to the rotor and a second side which, in an assembled machine, faces the air gap. The first side of the body has a plurality of recesses therein for receiving a corresponding plurality of magnets. The recesses are shaped and arranged to separate the magnets from each other and maintain a consistent spacing between them. When the device is attached to the rotor the magnets are held in a fixed position against the rotor. The electrical machine may be a motor or a generator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims priority toU.S. patent application Ser. No. 12/598,652, filed on Mar. 1, 2010,which is a 35 U.S.C. §371 National Stage Application ofPCT/AU2008/000591, filed Apr. 29, 2008, which claims priority toAustralian Patent Application No. 2007902348, filed May 3, 2007, theentire content of each application is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to permanent magnet electricalmachines including a planar array of magnets. In particular, theinvention relates to a device for positioning magnets on a rotor of apermanent magnet electrical machine. The device is especially suited foruse in axial flux electric motors and it will be convenient to describethe invention in relation to that example application. It should beunderstood however that the device is also suitable for other forms ofelectrical machine that incorporate a planar array of magnets, such aslinear motors or generators.

BACKGROUND OF THE INVENTION

In a permanent magnet electric machine the magnets are often secured tothe rotor in a planar array by an adhesive. Positioning of the magnetson the rotor is a difficult and time consuming exercise because themagnets tend to be attracted to each other or repel each other,depending upon the orientation of the magnets. It is therefore importantthat the magnets be precisely placed in a position in which the magneticforces are balanced. For example, the magnets may be oriented at anequal distance from one another in an alternating pole configuration,i.e. North, South, North, South, etc. This arrangement would produce anattractive force between the magnets, which results in a net force ofzero on each magnet if the equal distance between magnets is carefullymaintained in a precarious equilibrium.

Given this issue, it is also important that the magnets be held in thatposition at least until the adhesive has properly cured. The curing timeof the adhesive thus makes handling of partially assembled rotors adelicate exercise because any movement of the magnets outside of theirideal positions will cause them to move further, until they eventuallycome together. It is therefore undesirable to handle partially assembledrotors before the adhesive is completely cured. This slows down theproduction process and/or requires a large amount of valuable work spaceto be dedicated to the storage of rotors whilst the adhesive cures.

In a rotating motor having magnets attached to a rotor, centrifugalforces on the magnets during operation of the motor tend to pull themagnets radially outward and away from the rotor. If the sole means bywhich the magnets are secured to the rotor is an adhesive, the speed ofthe motor is thus limited by the strength of the adhesive. In this typeof construction it is thus essential that the operating speed of themotor be kept well below a speed at which the centrifugal forcesgenerated upon the magnets would overcome the adhesive bond holding themagnets to the rotor. Failure of the adhesive bonds could cause themagnets to be dislodged and subsequently damage the motor.

Magnets used in electric motors may be coated or plated to preventcorrosion. Thus, any adhesive which is used to secure a magnet to arotor is in fact merely securing the anticorrosion coating or plating tothe rotor. The strength of the bond between the actual magnet and therotor is thus limited to the strength of the bond between theanticorrosion coating/plating and the magnet material. The use ofadhesive alone is therefore not ideal for securing magnets to a rotorbut it is still the norm.

With the foregoing difficulties in assembly and operation of permanentmagnet electrical machines in mind, there is a need for a device whichcould facilitate the positioning of magnets within a permanent magnetelectrical machine, such as a motor. It would also be desirable,although not essential, for the device to be able to remain within theassembled machine to assist in retaining the magnets to the rotor intheir correct positions, with or without the use of adhesive, duringoperation of the motor.

SUMMARY OF THE INVENTION

One aspect of the present invention accordingly provides a device forpositioning magnets in a planar array within a permanent magnetelectrical machine of the type having a rotor and stator with an air gapthere between. The device includes a body made of non-ferrous materialand has a first side which is attachable to the rotor and a second sidewhich, in an assembled machine, faces the air gap. The first side of thebody has a plurality of recesses therein for receiving a correspondingplurality of magnets. The recesses are shaped and arranged to separatethe magnets from each other and maintain a consistent spacing betweenthem. When the device is attached to the rotor the magnets are held in afixed position against the rotor.

The electrical machine may be a motor or a generator. The invention isapplicable to both types of machine. Suitable motors may include rotarymotors, in which a rotor rotates about an axis, or linear motors, inwhich a “rotor” moves linearly with respect to an elongate stationarystator. The term “rotor” is thus used more broadly in connection withthis type of motor because the rotor does not actually rotate. Rotarymotors may include axial flux motors, in which the flux in the air gapextends in a direction parallel to the axis of rotation. It is suggestedthat the more common radial flux machine in which the flux extendsradially from the axis of rotation does not benefit as highly from theinvention. In that case the magnets are not configured in a planar arraybut are configured in a circular array. This means that a part producedaccording to the invention would need to mate to a circular rotor andproject a circular face into the air gap, which leads to productiontolerance issues that are difficult to overcome. In the case of a planararray of magnets the invention results in a simple, flat shape which issubstantially easier to produce and use. Similarly, the invention may beapplicable to all types of generator that incorporate planar arrays ofmagnets.

The magnet positioning device in accordance with the invention providessignificant advantages over prior art methods used for securing magnetsto a rotor. The device includes recesses which may be specificallyshaped to closely conform to the shape the magnets. This preventsmovement of the magnets within the recesses and maintains a consistentspacing between the magnets, both during assembly of the rotor andduring subsequent operation of the machine.

In the latter regard, it is to be noted that if adhesive is also used tosecure the magnets to the rotor, the device may be removed from therotor after the adhesive has cured. Given that the device maintains aconsistent spacing between the magnets, there is now no danger of themagnets moving if the rotor is handled before the adhesive is properlycured. The device will retain the magnets in their correct positions.

Whilst the device may be removed from the assembled rotor, it is howeverpreferably that it remains in place after the motor is fully assembled.In this way, the device assists in securing the magnets to the rotorduring subsequent operation of the machine.

In a preferred embodiment, the device is designed for use in an axialflux rotary motor having a disc shaped rotor which is rotatable about anaxis. In this type of motor the rotor disc is spaced from the stator ina direction extending along the axis with an air gap then remainingbetween the stator and the rotor disc. In this embodiment, the body ofthe device may have an annular shape and the recesses for the magnetsmay be spaced about the annulus such that, in operation of the motor,the magnets are spaced around the axis of rotation.

Advantageously, connecting means are provided for attaching the body ofthe device to the rotor. In the case of an axial flux motor, theconnecting means may include a plurality of clips spaced around the bodyof the device so as to attach the body to the rotor disc. Preferably,the clips are positioned adjacent a peripheral edge of the body and areshaped to engage a peripheral edge of the rotor disc.

Preferably, the device includes locating means for aligning the body ofthe device relative to the rotor. If the machine is an axial flux rotarymotor, the locating means preferably includes at least one pinprojecting in an axial direction from the first side of the body forengaging with a corresponding aperture in the rotor disc. Thisarrangement thereby facilitates alignment of the body of the device withthe rotor disc. More preferably, the locating means includes at leastthree pins projecting in the axial direction from the first side of thebody for engaging with at least three corresponding apertures in therotor disc. In this embodiment, the pins may be configured to hold thefirst side of the body away from the rotor disc until the pins andcorresponding apertures are aligned. This also ensures accurateconcentricity of the magnet array with respect to the rotor disc.

In a preferred embodiment, the device also includes balancing means forenabling weights to be secured to the device and thereby allow anyimbalance in the rotor to be corrected. In the case of a radial fluxrotary motor, the balancing means may include an annular grove locatedaround a peripheral edge of the body of the device. The groove ispreferably provided with a cross sectional shape which is configured toenable weights to be inserted and retained within the annular groove.

Another aspect of the present invention provides a permanent magnetelectrical machine including a rotor, a stator, a plurality of magnetsand a device as described above for positioning the magnets on therotor. In such a machine the device may also serve to assist in securingthe magnets to the rotor during operation.

A further aspect of the invention provides a method of assembling arotor for a permanent magnet electrical machine. The method includes thesteps of

providing a rotor;

providing a magnet positioning device as described above;

providing a plurality of magnets;

inserting the magnets into the recesses in the first side of the body ofthe device;

bringing a ferrous object into contact with the second side of the bodyof the device such that the ferrous object is adhered to the device bymagnetic forces generated by the magnets and the magnets are held withinthe recesses by the magnetic forces;

attaching the first side of the body of the device to the rotor suchthat the magnets are held in a fixed position against the rotor;

and removing the ferrous object from the second side of the body.

This method facilitates the assembly of a rotor for a permanent magnetelectrical machine. The ferrous object serves to hold the magnets withinthe recesses of the positioning device whilst that device is beingaligned with, and ultimately attached to, the rotor. The ferrous objectmay be of any suitable form and could, for example, have an annularshape with an outer diameter similar to the outer diameter of thepositioning device. Alternatively, the ferrous object may be circularwith a diameter similar to that of the outer diameter of the positioningdevice. As a further alternative, if the assembly method is implementedby an automated machine, the ferrous object may be a component of themachine.

The magnets used in the electrical machines for which the presentinvention is applicable may be of any known type. There are howeveradvantages in using high power magnets made of rare-earth metals such asneodymium. These provide a magnetic force which is much greater thanconventional magnets for the same size and weight. It is for this reasonthat precise positioning of the magnets, especially during assembly of arotor, becomes important. The magnets tend to stick together when beinghandled and may be very difficult to separate by hand.

Having said that, it is also possible to use magnets which are initiallyprovided in an unmagnetised state and then subsequently magnetise themafter they have been placed into the positioning device, or possiblyafter the rotor has been assembled. In this instance a slightlydifferent assembly method may be employed to hold the magnets within thepositioning device as it is brought into contact with the rotor. Forexample, the ferrous object used in the assembly method described abovemay be replaced with a vacuum holding device.

To assist the further understanding of the invention, reference is nowmade to the accompanying drawings which illustrate preferredembodiments. It is to be appreciated that these embodiments are given byway of illustration only and the invention is not to be limited by thisillustration.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a bottom perspective view of a magnet positioning devicefor an axial flux rotary motor in accordance with a preferred embodimentof the present invention;

FIG. 2 shows a top perspective view of the magnet positioning device ofFIG. 1;

FIG. 3 shows a bottom perspective view of the magnet positioning deviceshown in FIG. 1 together with magnets inserted therein;

FIG. 4 shows a bottom perspective view of the magnet positioning deviceof FIG. 1 as attached to a rotor;

FIG. 5 shows a top perspective view of the magnet positioning device androtor shown in FIG. 4;

FIG. 6 shows a cross sectional side view of an axial flux rotary motorincorporating the magnet positioning device of FIG. 1;

FIG. 7 shows an exploded perspective view of the motor shown in FIG. 6;

FIG. 8 shows an top perspective view of an alternative rotor for anaxial flux motor;

FIG. 9 shows a bottom perspective view of an alternative magnetpositioning device for use with the rotor shown in FIG. 8;

FIG. 10 shows a top perspective view of the rotor of FIG. 8 togetherwith the magnet positioning device of FIG. 9;

FIG. 11 shows a top perspective view of a further alternative magnetpositioning device together with a rotor for an axial flux motor;

FIG. 12 shows a bottom perspective view of the magnet positioning deviceand rotor of FIG. 11;

FIG. 13 shows a top view of the magnet positioning device and rotorshown in FIGS. 11 and 12;

FIGS. 13A and 13B show cross sectional side views taken along lines A-Aand 8-8, respectively, in FIG. 13 (but excluding the shaft which isshown in the previous figures);

FIG. 14 shows a cross sectional side view of the magnet positioningdevice and rotor shown in FIG. 11;

FIG. 15 shows a cut away top perspective view of the magnet positioningdevice and rotor shown in FIG. 11;

FIG. 16 shows a perspective view of a rotor for a linear motor;

FIG. 17 shows a top perspective view of a magnet positioning device forthe linear rotor shown in FIG. 16;

FIG. 18 shows a bottom perspective view of the magnet positioning deviceof FIG. 17; and

FIG. 19 shows a top perspective view of the linear rotor shown in FIG.16 together with the magnet positioning device shown in FIGS. 17 and 18.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Initially, it should be understood that throughout this description theterms “top” and “bottom” are used merely for convenience to refer to theembodiments shown in the accompanying drawings. It should accordingly beunderstood that these terms have no relevance to the orientation of theactual apparatus as it may be manufactured or used.

FIGS. 1 to 7 of the drawings show a preferred embodiment of the presentinvention. In particular, FIGS. 1 and 2 show bottom and top perspectiveviews, respectively, of a magnet positioning device 1 for use in apermanent magnet axial flux electric motor 3, as shown in FIGS. 6 and 7.

The components of the motor can be best seen in the exploded view shownin FIG. 7. These components include a housing, incorporating end shields5 and 7 and a side wall 9, a stator 11 (although the windings are notshown in the drawings) mounted within the housing. A rotor disc 13 ismounted on a shaft 15 which is rotatable within the housing by means ofbearings 17 and 19. A wave washer 21 is also included between thebearing 17 and the end shield 5 so as to reduce noise produced by thebearing and promote quieter operation of the motor 3.

As can be seen in the cross sectional side view shown in FIG. 6, therotor disc 13 includes a plurality of permanent magnets 23, which arepreferably neodymium magnets. As can also be seen in FIG. 6, an air gapexists between the top face of the magnet positioning device 1 (attachedto the rotor disc 13) and a lower face of the stator 11.

Referring again to FIGS. 1 and 2, FIG. 1 shows a first side of the body25 of the magnet positioning device 1, which is attachable to the rotor13. A bottom perspective view of the rotor disc 13 attached to thepositioning device 1 is shown in FIG. 4 and a top perspective view isshown in FIG. 5.

FIG. 2 shows a second side of the body 25 of the magnet positioningdevice 1 which, in the assembled motor shown in FIG. 6, faces the airgap.

The body 25 of the magnet positioning device 1 is made of a non-ferrousand non-electrically conductive material, such as a plastic of asuitable type. Examples may include Nylon, which might be glass fiberfilled for increased strength or mineral filled for reduced cost. Thebody 25 of the device 1 is of an annular shape and the first side of theannulus includes a plurality of recesses 27. These recesses 27 areshaped so as to closely conform to the shape of the magnets 23. FIG. 3shows a bottom perspective view of the magnet positioning device 1together with magnets 23 inserted within the recesses 27. The closeconformity of the shape of the recesses 27 to the shape of the magnets23 serves to prevent the magnets 23 moving within the recesses 27. Themagnets 23 are therefore separated from each other and a uniform spacingis maintained between them so as to prevent the magnets 23 being drawntogether or being repelled.

As can be best seen in FIG. 1, the recesses are formed by a plurality ofribs 29 which extend between inner and outer support rings 31 and 33respectively. Together, these support rings 31 and 33 and separatingribs 29 form for a spider-like cage structure.

In the preferred embodiment shown in FIGS. 1 to 7, the body 25 of themagnet positioning device 1 includes connecting means for attaching thebody 25 to the rotor disc 13. The connecting means is provided in theform of a plurality of clips 35 spaced around a peripheral edge of thebody 25.

The body 25 of the magnet positioning device 1 also includes locatingmeans for aligning the body relative to the rotor disc 13. In theembodiment shown, the locating means includes four pins 37 projecting inan axial direction from the first side of the body 25. These pins 37engage with corresponding apertures 39 in the rotor disc 13 so as tofacilitate alignment of the body 25 with the rotor disc 13.

The body 25 of the device 1 also includes balancing means in the form ofan annular groove 41 extending around a peripheral edge of the body 25.The cross sectional shape of the groove 41 is configured to enableweights, such as metal balls or wire, to be inserted and retained withinthe groove 41. Any imbalance in the rotor 13 can thereby be corrected.

In the embodiment shown in FIGS. 1 to 7, the recesses 27 extend all theway through the body 25. However, the side wall of the recesses 27includes a projecting flange, or shelf formation, 43 which prevents themagnets 23 passing all the way through the body 25.

In an alternative embodiment, not shown, it is possible that therecesses may not extend all the way through the body so that the secondside of the body, facing the air gap, is fully covered.

A method of assembling a permanent magnet axial flux motor 3 will now bedescribed. Initially, the magnets 23 are inserted into the recesses 27from the first side of the body 25. Once all of the magnets 23 have beeninserted the positioning device 1 will appear as shown in FIG. 3.

The positioning device 1 (including magnets 27) and the rotor disc 13are then brought together but, before doing so, a ferrous object, suchas an annular metal disc 28 (shown in FIG. 3), is brought into contactwith the first side of the body. The magnets 23 will thus be attractedto the ferrous object and thereby be held within their respectiverecesses 27. In this way, the assembly (positioning device 1, magnets 23and ferrous object) can then be brought into contact with the rotor disc13 without the magnets 23 immediately being pulled out of the recesses27 by the rotor disc 13. As the two parts are brought together, thealignment pins 37 will contact the surface of the rotor disc 13. Thisallows relative movement between the two parts until the pins 37 arealigned with the apertures 39 in the rotor disc 13. Once they arealigned, the pins 37 will engage within the apertures 39 and theconnecting clips 35 will permanently attach the magnet positioningdevice 1 to the rotor disc 13.

Preferably, an adhesive is applied to the magnets 23, or to the rotordisc 13, before the parts a brought together. The magnet positioningdevice 1, together with the adhesive, would ensure that the magnets 23do not separate from the rotor disc 13 during operation of the motor 3.

In an embodiment not shown, it is possible that the connecting clips 35may be omitted. In this way, the magnet positioning device may beremovable from the rotor disc once the adhesive has properly cured.

Referring now to FIGS. 8 to 10, there is shown a simplifiedrepresentation of an alternative embodiment of the present invention.FIG. 8 shows a rotor 50 for an axial flux motor attached to a shaft 52.The rotor 50 includes four permanent magnets 54.

FIG. 9 shows a magnet positioning device 56 for use with the rotor 50shown in FIG. 8. The magnet positioning device 56 includes four recesseswhich are sized and shaped to conform to the magnets 54 shown in FIG. 8.FIG. 10 shows the magnet positioning device 56 brought together with therotor 50.

Referring now to FIGS. 11 to 15, there is shown a magnet positioningdevice 156, in accordance with a further alternative embodiment of theinvention, attached to a rotor 150 for an axial flux motor. FIG. 11shows a top perspective view whereas FIG. 12 shows a bottom perspectiveview. FIG. 13 shows a top view and FIGS. 13A and 138 showcross-sectional side views taken along lines A-A and B-B, respectively,in FIG. 13. For the sake of clarity, however, the shaft 152, to whichthe rotor 150 is attached, has been omitted in these Figures. FIG. 14shows a cross-sectional side view of the rotor and magnet positioningdevice and FIG. 15 shows a cutaway view of the same combination.

As in the embodiment shown in FIGS. 8 to 10, the rotor 150 is mounted ona shaft 152 and includes four magnets 154. However, in this embodimentthe magnet positioning device 156 includes connecting clips 158 spacedaround the periphery of the body of the positioning device 156 to attachit to the rotor 150. The magnet positioning device 156 also includeslocating pins 160 which engage in corresponding apertures 162 in therotor 150. The magnet positioning device 156 further includes an annulargroove 164 to enable weights to be inserted and retained therein so asto enable any imbalance in the rotor 56 to be corrected.

The method of assembly of the rotors shown in FIGS. 8 to 10 and 11 to 15is the same as the method involved in the assembly of the embodimentshown in FIGS. 1 to 7.

Referring now to FIGS. 16 to 19, there is shown a further embodiment ofthe present invention as applicable to a linear motor. FIG. 16 shows arotor for the linear motor. In this type of motor, the term “rotor”should be interpreted broadly to mean the moving part of the motor.Clearly, the rotor does not rotate in this instance but, instead,travels linearly with respect to a stator of the linear motor. The rotor350 includes permanent magnets 354.

FIGS. 17 and 18 show top and bottom perspective views, respectively, ofa magnet positioning device 356 in accordance with an embodiment of thepresent invention. The magnet positioning device 356 includes recesses358 therein for receiving corresponding magnets 354 as shown in FIG. 19.

Although preferred embodiments of the invention have been describedherein in detail, it will be understood by those skilled in the art thatvariations may be made thereto without departing from the spirit of theinvention or the scope of the appended claims. For example, theconnecting means could include clips, as shown in the embodimentsdescribed herein, but could alternatively be formed by thermaldeformation, ultrasonic welding or some other form of connection betweenthe magnet positioning device and the rotor. Similarly, the locatingmeans may be in the form of projecting pins, as shown in the embodimentsdescribed herein, but could alternatively be corresponding formationswithin the magnet positioning device and rotor. Such alternatives areconsidered to be clearly within the scope of the appended claims.

We claim:
 1. A magnet positioning device for positioning a planar arrayof magnets within an electrical machine, the machine including a rotorand a stator with an air gap there between, the device including a bodymade of non-magnetic and non-electrically conductive material and havinga first side which is removably couplable to the rotor and a second sidelocated opposite the first side, the first side of the body having aplurality of recesses therein for receiving a corresponding plurality ofmagnets, the recesses being shaped and arranged to separate the magnetsfrom each other and maintain a consistent spacing between them, suchthat when the device is coupled to the rotor the magnets are held in afixed position against the rotor.
 2. A device as defined in claim 1wherein the electrical machine is an axial flux rotary motor having adisc shaped rotor which is rotatable about an axis, the disc shapedrotor spaced from the stator in a direction extending along the axis todefine the air gap there between, the body of the device having anannular shape with the plurality of recesses spaced about the annulussuch that the plurality of magnets are spaced around the axis.
 3. Adevice as defined in claim 1, wherein the electrical machine is a linearmotor having a substantially rectangle shaped rotor which moves linearlywith respect to the stator, the body of the magnet positioning devicehaving a rectangular shape with the plurality of recess spaced linearlyalong the body.
 4. A device as defined in claim 1, further comprising aferrous object removably coupled with the second side of the body,wherein the ferrous object is adhered to the device by magnetic forcesgenerated by the plurality of magnets, and the plurality of magnets areheld within the recesses by the magnetic forces.
 5. A device as definedin claim 1 further including an annular ring for enabling weights to besecured to the device and thereby allow any imbalance in the rotor to becorrected.
 6. A device as defined in claim 4, wherein the annular ringis located around a peripheral edge of the body, the cross sectionalshape of the annular ring being configured to enable weights to beinserted and retained therein.
 7. A device as defined in claim 1,wherein the plurality of recesses do not extend all the way through thebody such that the second side of the body is fully covered.
 8. A deviceas defined in claim 1, wherein the plurality of recesses extend all theway through the body, and a side wall of each of the plurality ofrecesses includes at least one of a projecting flange and a shelfformation to facilitate preventing the plurality of magnets passingthrough the body.
 9. A device as defined in claim 1 further comprisingat least one clip spaced around the body to attach the body to therotor.
 10. A device as defined in claim 1, further comprising at leastone pin for aligning the body relative to the rotor.
 11. A device asdefined in claim 10, wherein the at least one pin projects in an axialdirection from the first side of the body for engaging with acorresponding aperture in the rotor to thereby facilitate alignment ofthe body of the device with the rotor.
 12. A device as defined in claim10, wherein the at least one pin includes at least three pins projectingin the axial direction from the first side of the body for engaging withat least three corresponding apertures in the rotor, the pins beingconfigured to hold the first side of the body away from the rotor untilthe at least three pins and corresponding apertures are aligned.
 13. Amethod of assembling a rotor for a permanent magnet electrical machine,the method comprising: providing a rotor; providing a magnet positioningdevice that includes a body having a first side and a second side, thefirst side comprising a plurality of recesses configured to receive aplurality of magnets; inserting the plurality of magnets into therecesses in the first side of the body of the magnet positioning device;and removably attaching the first side of the body of the magnetpositioning device to the rotor such that the magnets are held in afixed position against the rotor.
 14. A method as defined in claim 13further comprising bringing a ferrous object into contact with thesecond side of the body of the magnet positioning device such that theferrous object is adhered to the magnet positioning device by magneticforces generated by the plurality of magnets and the plurality ofmagnets are held within the recesses by the magnetic forces acting onthe ferrous object.
 15. A method as defined in claim 14 furthercomprising removing the ferrous object from the second side of the body.16. A method as defined in claim 13 further comprising contacting thesecond side of the body of the magnet positioning device with a vacuumdevice configured to generate a vacuum that facilitates holding theplurality of magnets within the plurality of recesses.
 17. A method asdefined in claim 13 further comprising removing the magnet positioningdevice from the rotor.
 18. A method in accordance with claim 13, furthercomprising applying an adhesive to at least one of the plurality ofmagnets and the rotor.
 19. An electrical machine comprising: a stator; arotor configured to rotate with respect to said stator, wherein saidrotor and said stator are separated by an air gap there between; aplurality of magnets; and a magnet positioning device comprising a bodyhaving a first side which is configured to be removably coupled to saidrotor, and a second side opposite said first side, said first side ofsaid body comprising: a plurality of recesses therein for receiving saidplurality of magnets, said plurality of recesses configured to separateeach magnet of said plurality of magnets from other magnets of theplurality of magnets, said magnet positioning device configured tosecure said plurality of magnets in a fixed position against said rotor.20. A machine as defined in claim 19, wherein the electrical machine isan axial flux rotary motor having a disc shaped rotor which is rotatableabout an axis, the disc shaped rotor spaced from the stator in adirection extending along the axis to define the air gap there between,the body of the device having an annular shape with the plurality ofrecesses spaced about the annulus such that the plurality of magnets arespaced around the axis.
 21. A machine as defined in claim 19, whereinthe electrical machine is a linear motor having a rectangle shaped rotorwhich moves linearly with respect to the stator, and the device having arectangular shape with the plurality of recess spaced linearly along themagnet positioning device.
 22. A machine as defined in claim 19, furthercomprising a ferrous object removably coupled with said second side ofthe body, wherein said ferrous object is adhered to said magnetpositioning device by magnetic forces generated by said plurality ofmagnets, and said plurality of magnets are held within the recesses bythe magnetic forces.
 22. A machine as defined in claim 19 furthercomprising at least one clip spaced around the body to attach the bodyto the rotor.
 23. A machine as defined in claim 19 further comprising atleast one pin that projects in an axial direction from the first side ofthe body for engaging with a corresponding aperture in the rotor tothereby facilitate alignment of the body of the magnet positioningdevice with the rotor.
 24. A machine as defined in claim 23, wherein theat least one pin includes at least three pins projecting in the axialdirection from the first side of the body for engaging with at leastthree corresponding apertures in the rotor, the pins being configured tohold the first side of the body away from the rotor until the at leastthree pins and corresponding apertures are aligned.